(a) Field of the Invention
The present invention generally relates to a precoding method and apparatus.
(b) Description of the Related Art
When a plurality of transmit nodes communicate using the same resources, each transmit node precodes a transmit signal to reduce the influence of an interference signal. The precoding means applying a precoder to the transmit signal. The precoder may be called as a precoding matrix, a precoding vector, a beamforming matrix, or a beamforming vector.
Algorithms in which each transmit node calculates the precoder by using only partial information of entire channel information of a network using the same resources, calculates a corresponding receive filter, and updates the precoder in accordance with the receive filter have been developed. The transmit node preforms repetitive calculations to determine the precoder.
According to these algorithms, all transmit nodes receive channel information required for calculating the precoder from the receive nodes. Since instantaneous channel information is required for the repetitive calculations, a feedback cycle is reduced such that the amount of the feedback increases if a time-variant rate increases according to movement of the node or change of the communication environment. Further, additional calculation increases such that a substantive increase of information data rate is reduced.